Environmental effects on fibre reinforced polymeric composites: Evolving reasons and remarks on interfacial strength and stability

• Fibre reinforced polymeric composite interface strength and reliability
• Moisture diffusion theory and its effects
• Interfacial instability by environmental conditionings
• Fibre/polymer interface integrity and its effects on structural stability
• Thermodynamics behind the polymer nanocomposites

The interface between fibre and matrix of fibrous polymeric composites is most critical and decisive in maintaining sustainability, durability and also reliability of this potential material, but unfortunately a comprehensive conclusion is yet to meet the label of confidence for the engineering viability. Fiber reinforced polymer (FRP) composites are being accepted and also utilized as better and reliable alternative materials for repairing and/or replacing conventional materials, starting from tiny objects to mega structure in various engineering applications. The promise and potential of these materials are sometimes threatened in speedy replacement of conventional materials because of their inhomogeneities and inherent susceptibility to degradation due to moist and thermal environments. Environmental conditioning is traditionally believed to be a physical phenomenon but present literature has revealed that the interdiffusion between fiber and polymer matrix resin comprises of physical, chemical, mechanical, physico-chemical and mechano-chemical phenomena. The failure and fracture behavior at ambient conditions itself is a complex phenomenon till at present. The service conditions which are mostly hygrothermal in nature, along with a variation of applied loads make the mechanical behavior nearly unpredictable, far off from conclusions in evaluating the short term as well as long term durability and reliability of FRPs. It is essential to accurately simulate the initial and subsequent evolution process of this kind of damage phenomena, in order to explore the full potential of the mechanical properties of composite laminates. The present review has emphasized the need of complying scattered as well as limited literature on this front, and has focused on creating the urgency to highlight the importance of judicious uses of these materials with minimum safety factors with an aim to achieving lighter weight in enhancing specific properties.

The percentage of ILSS value decreases during above-ambient temperature testing in every mode of loading rate ranges because of thermal conditioning effect leading to spreading of process zone in the matrix resin which imparts high fibre/matrix debonding in glass/epoxy composites shown in the figure below.The changes occurring at the interface are highly sensitive and susceptible to the degradations under different environmental conditionings. Since the interphase is a region of chemical inhomogeneity, it provides an easy path to the system for becoming more susceptible to thermal, chemical, thermochemical and mechano-chemical degradations.Figure optionsDownload as PowerPoint slide